Spectroscopy of Pressure- and Field-Induced Insulator-Metal Transitions: Exploring Charge- and Spin-Organization in Complex Oxides and Magnetic Semiconductors

现在有强有力的证据表明，相关系统所表现出的一些最科学有趣和技术上最有前途的现象发生在低温相界附近。 这些现象包括中尺度电荷、自旋和轨道结构的自发组织，以及物理性质对外加压力和磁场的“巨大”敏感性。 要更好地理解这些奇特的现象，需要更深入地了解这些材料的低温相变过程中低能动力学性质是如何演变的。 这个个人研究者奖支持研究，利用一种独特的方法，使用非弹性光散射光谱探索-在以前不可能的方式-相关系统的自旋，电荷和晶格动力学的重要演变，而压力和/或场调谐通过低温相变。 本研究的主要重点将是两类现象：（A）复杂氧化物中的量子相变，以研究低温相变附近自发电荷，自旋和轨道组织的演变和影响。 (B)磁性半导体中的自旋电子学，探索相变附近磁性团簇形成的演化和影响。 这项研究不仅将提供有关技术上重要的材料的各种低温相变附近的动力学的关键信息，而且将使科学界更好地了解应用低温/高压光散射研究相变和极端相态的局限性和好处。 此外，该项目还将培养研究生和博士后研究人员掌握尖端的压力和光谱技术，最终增加该国的技术基础。最近的密集研究发现了各种功能材料，这些材料表现出具有技术前景的重要科学现象，例如，在磁存储设备，磁传感器，开关等。这些奇异的属性包括非常大的敏感性的电性能的磁场应用（“巨大的”磁阻），和突然的磁场和压力之间的敏感性转变导电和非导电阶段。 现在人们认为，这些奇特的性质可能是由纳米级结构的自发形成引起的，当这些材料在导电和非导电相之间过渡时;然而，在科学家能够理解如何最好地设计这些材料以获得技术优势之前，这种因果关系的性质需要得到显着阐明。 这个个人研究项目将利用一种独特的方法，其中激光用于研究纳米尺度结构的磁场和压力依赖性演变如何在复杂氧化物和自旋电子材料中产生戏剧性和技术上有用的特性。 本项目将获得的信息是有效设计和利用这些材料作为器械的必要先决条件。 此外，该项目还将培养研究生和博士后研究人员掌握尖端的压力和光谱技术，最终增加该国重要的技术基础。

There is now strong evidence that some of the most scientifically interesting and technologically promising phenomena exhibited by correlated systems occur near low temperature phase boundaries. These phenomena include the spontaneous organization of mesoscale charge, spin, and orbital structures, and "colossal" sensitivities of physical properties to applied pressure and magnetic field. A better understanding of these exotic phenomena demands greater insight into how the low energy dynamical properties evolve across the low temperature phase transitions of these materials. This individual investigator award supports research that utilizes a unique method for using inelastic light scattering to spectroscopically explore - in a way not previously possible - the important evolution of the spin, charge, and lattice dynamics of correlated systems while pressure- and/or field-tuning through low temperature phase transitions. The principle focus of this study will be on two classes of phenomena: (A) Quantum phase transitions in complex oxides, to study the evolution and effects of spontaneous charge-, spin-, and orbital-organization near low temperature phase transitions. (B) Spin electronics in magnetic semiconductors, to explore the evolution and impact of magnetic cluster formation near phase transitions. Not only will this research afford critical information about the dynamics near various low temperature phase transitions of technologically important materials, but it will provide the scientific community a greater understanding of the limitations and benefits of applying low-temperature/high-pressure light scattering for studying phase transitions and extreme phase regimes in a variety of systems. Further, this project will train graduate student and postdoctoral researchers in cutting-edge pressure and spectroscopic techniques, eventually adding to the technical base of the country.Intensive recent research has uncovered a variety of functional materials exhibiting scientifically important phenomena with technologically promising properties, e.g., in magnetic storage devices, magnetic sensors, switches, etc. These exotic properties include extremely large sensitivities of the electrical properties to the application of magnetic fields ("colossal" magnetoresistance), and abrupt magnetic field- and pressure-sensitive transitions between electrically-conducting and -non-conducting phases. It is now believed that these exotic properties are likely caused by the spontaneous formation of nanometer-scale structures when these materials transition between conducting and non-conducting phases; however, the nature of this causal connection needs to be significantly elucidated before scientists can understand how best to design these materials for technological advantage. This individual investigator research project will utilize a unique method in which laser light is used to study how the magnetic-field- and pressure-dependent evolution of nanometer-scale structures give rise to the dramatic and technologically-useful properties in complex oxides and spin-electronic materials. The information that will be obtained with this project is an essential prerequisite to the effective design and utilization of these materials as devices. Further, this project will train graduate student and postdoctoral researchers in cutting-edge pressure and spectroscopic techniques, eventually adding to the important technical base of the country.